This should work on my CentOS 6.6 but somehow the file name is not changed. What am I missing here?

rename -f  's/silly//'  sillytest.zi

This should rename sillytest.zi to test.zi but the name is not changed. Of course I can use mv command but I want to apply to many files and patterns.

There are two different rename utilities commonly used on GNU/Linux systems.

util-linux version

On Red Hat-based systems (such as CentOS), rename is a compiled executable provided by the util-linux package. It’s a simple program with very simple usage (from the relevant man page):

rename from to file...

rename will rename the specified files by replacing the first occurrence of from in their name by to.

Newer versions also support a useful -v, --verbose option.

NB: If a file already exists whose name coincides with the new name of the file being renamed, then this rename command will silently (without warning) over-write the pre-existing file.

Example

Fix the extension of HTML files so that all .htm files have a four-letter .html suffix:

rename .htm .html *.htm

Example from question

To rename sillytest.zi to test.zi, replace silly with an empty string:

rename silly '' sillytest.zi

Perl version

On Debian-based systems ,rename is a Perl script which is much more capable as you get the benefit of Perl’s rich set of regular expressions.

Its usage is (from its man page):

rename [ -v ] [ -n ] [ -f ] perlexpr [ files ]

rename renames the filenames supplied according to the rule specified as the first argument.

This rename command also includes a -v, --verbose option. Equally useful is its -n, --no-act which can be used as a dry-run to see which files would be renamed. Also, it won’t over-write pre-existing files unless the -f, --force option is used.